But the RMT, which represents conductors who are being transferred to the role of on-board supervisors as part of the changes, has yet to come to an agreement with GTR.

Both unions have raised safety concerns about the potential loss of a second safety-critical member of staff on Southern servcices as drivers would be responsible for opening and closing train doors.

Mick Cash, general secretary at the RMT, said: “RMT understands that central to the agreement with ASLEF is a guarantee of a second person ‎on the train.

“We also understand that the implementation of that aspect of the agreement is subject to further discussions and negotiations with RMT around the safety competencies of that second member of staff.

“It is now essential that we open up urgent ‎discussions with GTR around this core issue of the second safety-critical staff member, and the details of their future role, that will allow us all to move forwards. RMT is available for those talks with immediate effect.”

Then Charles Horton, chief executive officer at GTR, wrote to Mr Cash inviting the RMT to face-to-face talks next week to attempt to settle the dispute.

Mr Horton said his negotiating team was willing to meet next week ‘in a spirit of open and positive dialogue to explore the areas of difference between us with a view to resolving the dispute in the interests of our customers and employees’

Mr Horton also asked Mr Cash that ‘these discussions be conducted without the threat of further industrial action hanging over them’.

Mr Horton said: “We are pleased to have reached a deal with the ASLEF leadership. They were prepared to come to the table, with passengers liberated of any threat of strike action.

“Both parties arrived ready to listen, have an open mind and ready to do a deal and I am grateful to Mick Whelan and his Executive for the spirit they entered the talks and agreed a deal with us. I also recognise and respect that drivers will now vote on the agreement and I hope it will be given their green light.

“We would call on the RMT to follow that same consensual spirit and leadership and come to the table with the courage, confidence and conviction to settle their dispute for the benefit of passengers, the regional economy, their members and our employees”.

An RMT spokesman said: “We can confirm that we have had a formal offer of talks from GTR. That offer will be considered by RMT’s executive later today. The union will be making no further comment until the executive has met.”

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